The present invention relates to a magnetic disk drive, and more particularly to fixing construction of a spindle shaft for supporting a magnetic disk.
The magnetic disk drive includes a spindle motor for drivingly rotating a magnetic disk and a carriage for supporting a magnetic head that are mounted within a case composed of a base and a cover. The magnetic head is placed in a radial position over the magnetic disk by the carriage to write and read data thereto and therefrom.
A demand for the magnetic disk drives has increased and those applications expand from personal computers (PC) used in offices to laptop computers, portable equipment, vehicle-mounted car navigation systems and other outdoor devices. As a result, the use environment has become severe for the magnetic disk drives.
On the other hand, high-density recording and high-speed data transfer have been promoted, which require magnetic heads to have a higher degree of positional accuracy. It is essential to improve not only the reliability of mechanical systems under the usage environment conditions of drives but also the accuracy of components thereof. Further, even upon high-impact on a device, it is desired that a smaller effect be exerted on the various parts of the drive, and that the amount of displacement with several microns or so be not caused. In particular, it is desired for the shock not to produce a displacement of the magnetic disk, and a relative displacement between the magnetic disk and the magnetic head.
FIG. 6 shows the conventional fixing construction of a spindle shaft described in, e.g., Patent Document 1 (Japanese Patent Laid-open No. 10-125053). In this construction, the upper and lower portions of a spindle shaft 4 are screwed to a cover 2 and a base (not shown), respectively. Specifically, the base side end of the spindle shaft is fixed to the base with a plurality of screws, and the cover side end is fixed to the cover 2 with a single screw 16. Patent Document 2 (Japanese Patent Laid-open No. 2001-202682) discloses another conventional fixing construction in which first and second metal washers 27, 28 are fastened to a spindle shaft 4 with a screw 16 so that vibrations may be reduced which are caused by the rotation of a spindle motor and transmitted to a cover 2. Specifically, the cover 2 is formed with a hole at a position corresponding to the spindle shaft 4, the first metal washer 27 is placed on the cover in the periphery of the hole, and the second metal washer 28 is used to sandwich the cover 2 in the periphery of the hole in combination with the first metal washer 27.